If you are not able to eat much, then a substantial
proportion of the fluids you drink should contain electrolytes.Examples include non-caffeinated and non-diet
sodas, apple juice, Gatorade.There are
rehydration mixes available that contain the exact balance of electrolytes that
are best for the body.You should drink
at least 2-3 liters of fluid per day.

Vomiting complicates hydration strategies (see below).

If you are unable to take adequate fluids by mouth, then it
may be necessary to give them through an IV.